FUEL OXIDIZER REACTION PRODUCTS (FORP) CONTAMINATION OF SERVICE MODULE AND RELEASE OF N-NITROSODIMETHYLAMINE IN A HUMID ENVIRONMENT FROM CREW EVA SUITS CONTAMINATED WITH FORP

Abstract

The U.S. Control Moment Gyros (CMGs) maintain the International Space Station (ISS) vehicle attitude by compensating for disturbances. It is preferred to use CMGs, instead of attitude control thruster firings. However, prior to an extravehicular activity (EVA) on the Russian Segment (RS), the Docking Compartment (DC1) must be depressurized, as it is used as an airlock. When the DC1 is depressurized, the CMGs’ margin of momentum is insufficient to compensate for the disturbance and the service module (SM) attitude control thrusters need to fire to desaturate the CMGs. The SM roll control thruster firings induce fuel oxidizer reaction products (FORP) contamination of the adjacent SM surfaces. One of the components present in FORP is the potent carcinogen N-nitrosodimethylamine (NDMA). Since the EVA crewmembers often enter the area surrounding the thrusters for tasks on the aft end of the SM and when translating to other areas of the Russian Segment, the presence of FORP contamination is a concern. This paper will discuss FORP contamination of the SM surfaces, the potential release of NDMA in a humid environment from crew EVA suits, if they happen to be contaminated with FORP, and the toxicological risk associated with the NDMA release.